The Storm Prediction
Center (SPC) is the National Weather Service’s center of expertise
for forecasting convection, especially for economically-disruptive
weather events such as tornadoes, large hail, and damaging winds.
The current SPC severe thunderstorm forecast product suite includes
Convective Outlooks for today (Day 1), tomorrow (Day 2) and the day
following (Day 3). However, during the past couple of years, local
National Weather Service Offices have been issuing hazard weather
outlooks that sometimes mention the likelihood of severe storms out
to seven days in advance for their county warning area. In addition,
the emergency management community has expressed an interest in
longer range outlooks to facilitate planning.

This Product
Description Document concerns SPC issuance of Day 4-8 severe weather
outlooks to provide national guidance on a critical public safety
issue for media, emergency managers, local National Weather Service
Forecast Offices and ultimately the United States Public. This
product will help its customers to adequately prepare several days in
advance of an expected severe weather episode. This product
enhancement is aligned with the NOAA Strategic Objective for FY2005
-2010 to “Improve predictability of the onset, duration and impact
of hazardous severe weather and water events.”

This product is
currently available to only NOAA internet addresses, to collect
feedback on the content and value from NWS field forecasters. We are
now satisfied that the product is ready for a wider audience. During
its period of NOAA-only viewing, we have heard from several external
customers who would like us to expedite broader availability of this
enhanced severe weather service. Select feedback include

“Concerning the
experimental Day 4-8 Probabilistic Outlooks -- I am a degreed
meteorologist forecasting operationally for one of the nations larger
energy companies. Would it be possible for me to have access to these
products?”

Jacob Klee -
meteorologist for Dominion Power

I saw the link to
the outlooks 4-8 on the website but they are forbidden

to the general
public. I am writing to ask if and maybe when the public

can see them? …

M. Maxwell - USA
Weather

The
SPC proposes to make the probabilistic hazard information open to all
customers for comment through its web site beginning on October 3,
2005 and ending on 28 July2006 at which time a decision to
proceed with testing, revise the test or to continue on the path to
operational production will be made. Since the product would be in
the public domain, this outlook can be repackaged and re-transmitted
in accordance with standard NWS product use policies.

Comments:

During
the internet test the format for the information will be unchanged
from its current NOAA-restricted form unless internal or external
feedback results in product revision. An example can be found (by
NOAA users) in the convective outlook section of the SPC website each
day (for example see http://www.spc.noaa.gov/products/exper/day4-8/
). Given continued success, the SPC plans to eventually embed this
information in human and machine readable form within one or more of
its operationally disseminated AWIPS products. An NWS Public
Information Statement (PNS) Service Change Notification (SCN) will be
issued prior to AWIPS product modification.

Part
II - Technical Description

The
Day 4-8 Severe Weather Outlook product will consist of one graphic
with an area (s) where severe weather is anticipated during the
period. The severe weather threat areas will be depicted with a
closed line and a label indicating the dates of the expected threat.
A short 2-4 sentence paragraph will accompany the graphic to briefly
describe the area depicted and occasionally describe the key reasons
for the forecast. The forecast decision will be based on a variety
of guidance information including the GFS, UKMET and ECMWF
deterministic models, Medium Range (MREF) ensemble guidance and other
statistical techniques.

For
the remainder of FY05 the Day 4-8 severe weather outlook would be
available via internet (www.spc.noaa.gov),
however, given a successful internet test the information would
become an AWIPS transmitted product. These extended range severe
weather outlooks will provide SPC customers and partners with
information that will help them provide better public safety for the
United States public.